1. Field of the Invention
The present invention relates to an image forming apparatus having a finisher in which sheets of paper discharged from a copying machine or the like are distributed and stapled. More specifically, the present invention relates to an improved image forming apparatus having a finisher.
2. Description of the Related Art
Recently, in order to automatically handle sheets of paper in an image forming apparatus such as a copying machine, various optional devices such as an automatic document feeding apparatus (hereinafter referred to as an ADF) or a sorter for sorting and grouping copied or printed sheets have been developed and popularly used. One of such optional devices is a sorter having a finisher in which sheets of paper distributed and contained in a plurality of bins of a sorter are automatically stapled and stacked. Such sorter having a finisher has come to be used in some of the larger type copying machines.
In the conventional sorter having the finisher, one of the bins for sorting is used as a tray for normal copying in case where the finish mode is not selected. (Usually, the uppermost bin is used as the tray). When the machine is in the finish mode in which the stapling process is carried out, the sort bins are used for the stapling process. Therefore, the next copying operation, even when the copying machine is available for copying could not be executed until the end of the process in the finish mode.
Meanwhile, in the sorter having the finisher, the size of sheets for copying may be changed while the finish mode for the stapling process is selected and the image forming process is being carried out. In such case, even if the sheets of paper having the different sizes can be stapled, proper stapling process can not be carried out as the size of the sheets are various. Therefore, when the finish mode is successively selected, the stapling cannot be carried out in a satisfactory manner.
Now, image forming apparatuses having automatic magnification selecting function and automatic paper selecting function have been developed. The automatic magnification selecting function (hereinafter referred to as AMS) means a function for automatically setting the most suitable copying magnification rate at which the whole original images are properly formed on a sheet having the selected size and there is no possibility of some portions of the images being out of the paper, based on the size of the original (which is normally detected automatically in the ADF) and on the size of the sheet (in this case, selected by an operator). The automatic paper selecting function (hereinafter referred to as APS) means a function of automatically selecting a paper feeding portion containing sheets of paper whose size allows proper formation of original images at a selected copying magnification rate without the possibility of some portions of the images being out of the paper, based on the above mentioned size of the original and the copying magnification rate (in this case, selected by an operator).
Therefore, when originals having different sizes are set in the ADF at one time, the APS mode and the said finish mode are selected and the image forming process is carried out, then sheets of different sizes are selected and fed corresponding to the size of the originals to be transferred to the finisher. Consequently, the stapling process is carried out with the size of sheets being various.